The global total solar radiation energy is about 1.7×1017 W, whose 1% belongs to China (1.8×1015 W, equivalent to 1,900,000 million tons of standard coal per year), and it is 680 times of annual total energy consumption in China. Electricity is the most consumed secondary energy. Solar power generation technology is an effective way to relieve the current energy crisis and it has a very extensive application prospect.
The solar power generation technology is usually classified into photovoltaic (PV) power generation and solar thermal power generation. The PV power generation is mainly based on the photoelectric effect of the photovoltaic cell panel. However, this technology mainly has three drawbacks: (1) power generation varies with the solar intensity, and the power cannot be generated in the night and rainy days, which will greatly affect the power grid; (2) since the solar flux density is low, the area of the required PV cell panel for unit power generation capacity is large, and the production process of the PV cell causes serious pollution and high cost; (3) the solar spectral response bands of the PV panels are mainly concentrated in the high frequency region (400<λ<1100 nm) and the power of the low frequency region is mostly transformed into heat, which increases the temperature of the PV cell and decreases the photoelectric conversion efficiency and the service life. The PV power generation technology itself is difficult to overcome the problem of discontinuous power generation at day and night, and is usually equipped with storage batteries or an energy-storage generating system (such as storage hydropower station), so that the cost will be very high.
The solar thermal power generation is mainly classified into solar trough thermal power generation, solar linear Fresnel thermal power generation, solar tower thermal power generation, and solar dish thermal power generation. The fundamental principle for the solar thermal power generation is to focus the sunlight by parabolic reflectors (trough concentrators, linear Fresnel concentrators, heliostats and dish concentrators), and to produce steam or heat other fluid by photothermal conversion or heat exchangers, so as to drive the heat engine to generate power. The advantage of this technology is that the whole band of sunlight can be absorbed, and the continuous power generation is available by using thermal energy storage or by fuel supplement.
The heat engine used in the conventional solar thermal power generation systems is steam turbine, whose system is complex and has a low efficiency. The gas turbine system is also a heat engine and a simple gas turbine system consists of a compressor, a combustion chamber and a gas turbine. The gas turbine system has many advantages, such as high specific power, low vibration noise, long service life and easy maintenance. However, the simple gas turbine cycle has a low cycling efficiency and the heat loss of exhaust gas is large, for which the simple gas turbine is usually combined with Rankine cycle to promote the overall system efficiency.
A common solar power gas turbine system adds a solar air receiver to the simple solar gas turbine system, in which the compressed air from the compressor is preheat by a solar air receiver, and then enters the combustion chamber to produce high temperature gas which finally drives the gas turbine to work.
Compared with the simple gas turbine system, the solar gas turbine system increases the heat of the air entering the combustion chamber to reduce the fuel consumption. However, whether it is a simple gas turbine system or a solar gas turbine system, exhaust gas temperature of its gas turbine is very high and heat loss is very large. Although the combined gas-steam cycle system can be used to improve system efficiency, it's too complicated in technology and high in cost.